We conducted our studies using 3 cell lines that represent 3 distinct types of breast cancer: ZR75-1 cells are luminal ER/PR+Her2+AR+ cells, BT549 cells are mesenchymal-like ER/PR-Her2-AR+ cells and MDA MB 231 cells are mesenchymal stem-like ER/PR-Her2-AR- cells. This evidence concerns the gene ESR1 and breast cancer.